Echidna

Japanese: Echidna

…The dog that guards the gates of the underworld in Greek mythology. In Hesiod's Theogony, the dog is said to be the son of the monsters Typhon and Echidna, with 50 heads and a bronze voice, but in classical literature and art, it is depicted as having three heads and a snake's tail, and it is the latter that has been passed down to Christian art. The story of Hercules descending into the underworld, capturing Cerberus alive and bringing him back to earth is famous as one of his twelve labors. …

From [Typhon]

...The eruption of Mount Etna is said to be the work of Typhon, who was trying to escape this pressure. Typhon is also said to have mated with Echidna, a monster with the upper body of a woman and the lower body of a snake, and became the father of monsters such as the Chimera, the Lerna Hydra (water snake), Cerberus, the guard dog of the underworld, and the Sphinx. [Tomohiro Mizutani]...

*Some of the terminology that mentions "Echidna" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

Japanese:

…ギリシア神話に登場する冥府の門の番犬。ヘシオドスの《神統記》には，この犬は怪物テュフォンとエキドナEchidnaの子で，50の頭と青銅の声をもつと語られているが，古典期の文学や美術では，頭は三つで，蛇の尾をもつ姿に描かれており，キリスト教美術に受け継がれたのも後者の方である。ヘラクレスが冥府に下り，ケルベロスを生捕りにして地上に連れ戻った話は，彼の十二功業の一つとして名高い。…